Project Summary The research proposed in this application will focus on understanding how colonic stem cells function in repair after epithelial injury. It is known that epidermal growth factor receptor (Egfr) signaling is activated after injury and this contributes to repair; however, this activation and subsequent growth and proliferation, must be tightly regulated to avoid aberrant overgrowth. We have found that an Egfr inhibitor, Lrig1, marks a population of colonic stem cells our proposal seeks to clarify the role of Lrig1+ stem cells in wound healing. Currently, it is relatively unknown which specific colonic progenitor cell populations are responsible for regenerating an epithelium damaged colitis. To understand this, we have executed a series of short-term lineage-tracing experiments in mice undergoing oral administration of dextran-sodium-sulfate (DSS), proposed in our NIDDK Mentored Research Scientist Award (K01) grant. By directly observing Lrig1+ progenitor cell activation during colonic injury repair, via short-term lineage tracing experiments, it is readily apparent that Lrig1+ progenitor cells are responsible for generating large numbers of cells in the damaged colonic epithelium. Interestingly, Lrig1+ progenitor cell activation appears to originate around the +4 position of the colonic crypts, which is distinct from the pattern observed from Lrig1+ cells in the crypt-base in uninjured states. These observations suggest that Lrig1 is important in those cells present in the +4 region, independent from it?s role in the crypt-base compartment, and this is perhaps crucial for colonic regeneration and repair. The studies proposed here seek to understand the transcriptomics of these Lrig1+ progenitor cells as fundamental drivers of colonic regeneration and repair. These studies are a clear ?next step? to the studies we have proposed and conducted under our NIDDK Mentored Research Scientist Award (K01) grant.